These long-lasting pollutants, known as the”dirty dozen,” include DDT, which was used for decades for pest control in farming and for public health, and PCBs, used in coolants and as plasticizers in paints and cements. Both were banned in the 2001 international Stockholm Convention because of adverse health and environmental impacts.

Since the early 1990s levels of POPs have been decreasing as nations phased out their uses. But starting in the early to mid-2000s, POPs concentrations in the atmosphere again began to climb. The researchers found that in years of high temperatures with less sea ice, atmospheric levels of POPs have increased. They have gone back down again in cooler years of more expansive ice.

“These chemicals are semi-volatile, meaning they don’t stay in the air forever,” Hayley H. N. Hung, a scientist at Environment Canada and co-author of the study, told SolveClimate News. “They drop down and get deposited into different materials.”

The organically rich, cold soil of the Arctic has trapped these chemicals for decades, while the polar oceans have contained them with sea ice. This “literally puts a lid on the pollutants to keep them in place,” Hung said to SolveClimateNews.

When the ice melts, the POPs are ‘uncapped’ and re-enter the atmosphere. The revolatilization of these chemicals endangers the global food chain as they bioaccumulate from lower to higher species. Cancers, allergies, damage to central and peripheral nervous systems, and disorders of the reproductive and immune systems are just some of the potential health impact unleashed on animals and humans.

As the past catches up to the future, the authors warn that Arctic warming could undermine global efforts to reduce exposure to these harmful chemicals.